Small unmanned aircraft, and in particular unmanned aerial vehicle (UAV) type helicopters, require light-weight, low cost electric driven gearbox assemblies. A gearbox is designed to take power generated by the electric motors and convert it to rotational force imparted on the main rotor. The same gearbox may also be configured to drive the tail rotor together with the main rotor.
The use of multiple electric motors results in more power being generated from two smaller motors, as opposed to a single larger motor. The component most likely to fail in operation is one or more electric motors. Thus, whether employing one or multiple motors, the failure of any single motor during active operation can lead to serious component damage in the best of cases, and utter and complete system failure (i.e., a crash) in a worst case scenario.
The inability to identify and decouple (in real time) the failed electric motor while that motor is operational has proven to be a difficult challenge.
For many years, piloted helicopters were required to employ multiple motors (each usually large gas-driven engines weighing hundreds of pounds) as a safety measure. Complicated clutching mechanisms, which in turn also added significant additional weight to the already heavy power trains became a necessary evil.
Despite the heavy weight and cumbersome design nature of traditional piloted helicopter power trains, depending on the root of the failure, de-clutching of a failed engine section was simply not always possible.
Nevertheless the need to be able to declutch a failed section is important even in large aircraft. The idea of using multiple engines to drive a single main rotor has been adopted in single propeller driven fixed wing aircraft. In addition to being able to declutch a failed engine, the approach used in early manned (piloted) helicopter design was adopted in winged aircraft to convert twin-engine propeller-driven airplanes to single propeller multi-engine configurations. One such example is described in U.S. Pat. No. 4,829,850 to Soloy. An example perspective view of a gearbox assembly of Soloy is shown in prior art FIG. 1A. The corresponding gear train assembly is shown in prior art FIG. 1B.
The Soloy gearbox assembly shown has been adapted to date solely for use with gas-driven engines. The decoupling approach remains a problem as it requires use of a complex clutching mechanism.
With the proliferation of light-weight, special purpose application UAVs becoming popular for wide scale military and commercial applications, but also for use by hobbyists, size and weight restricted design approaches make the Soloy approach impractical.
In a UAV configuration, for example, it is common to integrate an entire power train of the UAV—including all the motors, gearbox assembly, and drive shaft torque generation—as a self-contained solution, in some cases marketed or promoted as an off-the-shelf turn-key solution, ready to install on a UAV.
The entire power train design constraints provided that any multi-motor design (including housing plates, screws, spacers and other design construction related components) weigh from a few pounds at best to no more than a few tens of pounds as a worst case scenario. Clutching mechanisms are simply not feasible. Failed motors must decouple safely and quickly. The challenge to design a new power train which uses multiple motors, each of which can safely and quickly decouple in event of motor failure remains a huge challenge in the UAV arena.
A design configuration that could inherently provide scalability in terms of providing a way that allows a designer to accommodate more than two motors, introduced another layer of complexity.
The ability of a power train design to be employable in non-helicopter type UAVs would allow for mass production leading to lower costs and more commercially available off the shelf design configurations for a variety of uses and UAV applications. Increased application usage should lead to better design and construction which translates into greater reliability overall and may also mean better quality of construction. It also means greater demand and faster consumer adoption of UAVs (drones) generally.